Tetracycline (Tc) is an inexpensive and effective broad spectrum antibiotic which has been extensively used in antimicrobial therapy. Tc along with scaling and root planing has been used in treating the complex microbial flora found in periodontal disease. Previous work has been shown that Tc therapy for periodontal disease selects for Tc resistant oral streptococci. Recently we have found that high level tetracycline resistance (Tc/r) in genital bacteria is strongly associated with the streptococcal tetM resistance determinant. We will determine the prevalence of (Tc/r) in oral microrganisms, other than streptococci, in periodontal patients before, during and after Tc therapy. We will determine the mechanism of Tc/r using molecular probes. We will determine if tetM or other well characterized Tc determinants are present. We will identify the Tc/r bacteria by gram stain, cultural and biochemical characteristics and locate the Tc determinant (plasmid vs chromosomal) in the various strains. This pilot study will determine if other oral bacterial species have become Tc/r, what proportion carry tetM and how Tc usage effects there numbers.